The invention relates to light-emitting keys, in particular to light-emitting keys having multiple independently-illuminated messages for equipment panels, in particular in the aviation or automotive industries.
The term xe2x80x9cmessagexe2x80x9d is used to designate any type of pattern, of symbolic or alphanumeric type, generally carried on the front face of a key or a button, indicating the function of the button and, where appropriate, the state of one or more actions controlled by said key or said button.
Light-emitting keys used for aviation equipment must perform several functions in spite of their small size, which contributes to presently-encountered keys being complex. These keys must simultaneously provide both an electrical contact by applying pressure on a contactor installed on the panel, and also information by means of light signaling, in general making use of a transparent front face fitted with a message-forming mask, which is back-lit by internal lighting.
With some keys, it is advantageous to be able to have at least two different sources of light, so as to be able to illuminate two or more different messages selectively, e.g. ON and OFF, with ON being illuminated in green and OFF in red. This kind of key is referred to herein as a light-emitting key with multiple independently-illuminated messages. The light sources can be of the same color or of different colors.
Keys are known that comprise a base fitted with an electrical contactor and at least two light sources, and including a pushbutton in register with the contactor and the light sources, said button projecting from the panel. Reference can be made to document U.S. Pat. No. 3,093,718, for example. The button is constituted by a rigid body made by injection molding, which body has an internal housing for a pusher fitted with a spring forming resilient button return means and actuating the contactor. The front face of the button is closed by a label (or xe2x80x9cslidexe2x80x9d) carrying the two messages for illumination in the form of transparencies. The inside of the button body is partitioned so that each light source illuminates only one message. The inside of the button body is generally painted white so as to improve light diffusion. In addition, a gasket is fitted around the button body so as to be clamped between the button body and the panel.
The structure of such a key makes use of numerous parts, thereby making the product expensive to manufacture and to maintain. In addition, building up strips of keys on a common base is difficult. Furthermore, such keys are not completely leakproof and moisture can infiltrate between the button body and the panel in spite of the sealing gasket.
Document U.S. Pat. No. 4,535,396 describes a pushbutton of design analogous to the above pushbutton, but made in simpler manner. It comprises a partitioned cage having two translucent blocks engaged therein, the cage being inserted in a body between a slide and a light-emitting diode (LED) support, and the end result forming a rigid assembly that is associated with a return spring. In that arrangement, the translucent block performs an optical function only.
Also known are keys comprising a button that is integral with a bearing rim, to which it is connected by a flexible peripheral ligament forming the resilient return member. Electrical contact is obtained by the presence of an internal central finger integrally molded with the button and pressing against an electrical contactor carried by the panel. To obtain light-emitting keys, that type of button is molded out of a translucent material, and then its outside is painted black. The front face is then etched or fitted with a slide, e.g. by adhesive. A light-emitting key is thus obtained very simply. Unfortunately, it is not possible with that kind of key to obtain independent illumination of a plurality of messages, because the transparency of the material used would mean that the various light sources would illuminate all the messages carried by the front face equally, giving rise to confusion as to the message being signaled.
The state of the art is also illustrated by document JP-A-1 173 838. That document describes a pushbutton having a unitary element of flexible design, comprising a bearing rim and a hollow key body connected by a peripheral ligament, the body being compartmentalized by a central partition. Nevertheless, the key body is covered in a rigid cap, whose presence is made necessary by the absence of a translucent block inside the key.
Reference can also be made to document JP-A-01 211 195 which describes an analogous arrangement.
An object of the invention is to provide a light-emitting key with multiple independently-illuminated messages and that does not present the above-mentioned drawbacks and limitations.
More particularly, the invention provides a light-emitting key with multiple independently-illuminated messages for fitting to an equipment front panel, in particular for aviation equipment, the key comprising a bearing rim and a hollow key body terminated by a front, drive face covered by a mask etched with messages to be illuminated, said key body being connected to said bearing rim by means of a peripheral ligament, said body, said ligament, and said rim being made as a single piece of flexible material. According to the invention, a slab of translucent material subdivided into blocks by at least one opaque partition extending substantially perpendicularly to the front face is received inside the key body so as to extend as far as the front, drive face of the key.
The translucent block of the above-mentioned light-emitting key serves not only to convey light, but also to stiffen the body of the key which is of flexible design, thereby eliminating the need for a rigid cap.
Thus, if the panel is fitted with two different light sources, each block channels the light from one of the sources independently, with each light path being separated from the other by an opaque partition. Each source can thus illuminate a different message forming part of a common mask, each message being in register with one of the blocks.
Advantageously, the bearing rim is shaped to present a peripheral projection projecting towards the front panel and acting as a sealing gasket. Sealing is thus provided without it being necessary to fit a gasket.
In a first embodiment of the key, the blocks are joined together at the front face.
The opaque partition separates them, but the blocks are always held together by a thin ligament sandwiched between the partition and the mask. This makes the blocks easier to handle during manufacture of the key, particularly when more than two blocks are used. In addition, the above-mentioned ligament reinforces the front face of the key body.
In a variant embodiment, the blocks are separate. The two light paths are thus totally separated, optically, since the opaque partition can extend as far as the mask.
In a first aspect, the mask is a label carrying the messages to be illuminated as transparencies.
This makes it very easy to fit the mask on the front face, thus making it possible to produce light-emitting keys that are all the same and to distinguish them by the labels they carry.
In a second aspect, an opaque covering covers the drive face, allowing the messages for illumination to show through in the drive face.
The messages are easily obtained by laser etching methods. Depending on circumstances, these messages can be invisible when the light is out, or they can be made legible in daylight by means of a translucent paint.
For keys of the type including an internal finger for driving an electrical contactor of the panel, the finger is advantageously carried by the opaque partition.
In a first method of manufacturing the key, the blocks are secured in the key body by means of adhesive.
In a second implementation, the blocks snap-fasten in the key body.
In a third implementation, the key body and its partition(s), together with the associated bearing rim, are overmolded onto the blocks, being made of a material that is opaque.
The invention also provides a strip of light-emitting keys, the strip being constituted by a plurality of juxtaposed keys presenting at least one of the above-specified characteristics, the bearing rim of said keys forming a peripheral bearing rim for said strip.